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一、（I/O）流递归复制一个文件

第一种：

else if语句过多，看起来冗余，优点：多级文件一次性复制完整

import java.io.*;//数据源：src/main/java/day15_8_13/haha
//目标;src/main/java/LaJi
public class DiGuiCopy {public static void main(String[] args) throws Exception {File file = new File("src/main/java/day15_8_13/haha");File file1=new File("src/main/java/LaJiZhan");diguiCopy(file,file1);}public static void diguiCopy(File file,File file1)throws Exception{if(file.isDirectory()&&file!=null){File file2s = new File(file1.getPath() + "\\" + file.getName());System.out.println("新文件夹创建："+file2s.mkdir());File[] files = file.listFiles();if(files!=null){for (File file2 : files) {if(file2.isFile()){diguiCopy(file2,file2s);}  else if (file2.isDirectory()) {diguiCopy(file2,file2s);}}}} else if (file.isDirectory()&&file==null) {//在目标文件下创建相同名字的文件File file2s = new File(file1.getPath() + "\\" + file.getName());System.out.println("新文件夹创建："+file2s.mkdir());} else if (file.isFile()&&file!=null) {File file2s = new File(file1.getPath() + "\\" + file.getName());System.out.println("新文件创建："+file2s.createNewFile());//创建字节输入流，创建字节输出流BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(file2s));byte[] bytes = new byte[2048];int len=0;while ((len=bis.read(bytes))!=-1){bos.write(bytes,0,len);bos.flush();}  bos.close();System.out.println("写入成功");} else if (file.isFile()&&file==null) {File file2s = new File((file1.getPath() + "\\" + file.getName()));System.out.println("空文件创建："+file2s.createNewFile());}}
}

第二种：

如果第一次文件内容未写成功，就运行一次，优点：避免多次if/for死递归出错，代码清晰

import java.io.*;/*
复制文件夹src/main/java/day15_8_13/haha下面所有文件和子文件夹内容到src/main/java/day15_8_13/haha_A*/
public class DiGuiCopy1 {public static void main(String[] args) {//将目标文件夹封装成File对象File file = new File("src/main/java/day15_8_13/haha");
//        String path = file.getPath();
//        System.out.println(path);fun(file);}public static void fun(File file) {File[] files = file.listFiles();for (File file1 : files) {if (file1.isDirectory()) {String filePath = file1.getPath();String newPath = filePath.replace("haha", "haha_A"); //src/main/java/day15_8_13/haha//目标文件夹File file2 = new File(newPath);file2.mkdirs();fun(file1);} else {//file1  原本的文件String parent = file1.getPath();String newPath = parent.replace("haha", "haha_A");//src/main/java/day15_8_13/haha_AFile file2 = new File(newPath);write(file1, file2);}}}public static void write(File p, File s) {try {BufferedInputStream bis = new BufferedInputStream(new FileInputStream(p.getPath()));BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(s.getPath()));
//            BufferedReader br = new BufferedReader(new FileReader(p.getPath()));
//            BufferedWriter bw = new BufferedWriter(new FileWriter(s.getPath()));byte[] bytes = new byte[2048];int length = 0;while ((length = bis.read(bytes)) != -1) {bos.write(bytes,0,length);bos.flush();}bos.close();bis.close();} catch (Exception e) {e.printStackTrace();}}
}

二、（I/O）流递归删除一个文件

import java.io.*;import static day15_8_13.DiGuiCopy.diguiCopy;
//缺点：删除后，还会留存空的根目录
public class DiGuiDelete {public static void main(String[] args) throws Exception {File file=new File("src/main/java/LaJiZhan/haha");diguiDelete(file);}public static void diguiDelete(File file){if(file.isDirectory()&&file!=null){File[] files = file.listFiles();if(files!=null){for (File file1 : files) {if(file1.isFile()){diguiDelete(file1);}  else if (file1.isDirectory()) {diguiDelete(file1);}}} else if (files==null) {diguiDelete(file);}} else if (file.isDirectory()&&file==null) {//在目标文件下删除相同名字的空文件System.out.println("空文件夹删除："+file.delete());} else if (file.isFile()) {System.out.println("文件删除："+file.delete());}}
}